1. Field of the Invention
The present invention relates to a substrate treatment apparatus and a substrate treatment method for cleaning substrates. Substrates to be treated include semiconductor wafers, substrates for liquid crystal displays, substrates for plasma displays, substrates for FEDs (Field Emission Displays), substrates for optical discs, substrates for magnetic discs, substrates for magneto-optical discs, substrates for photomasks, etc.
2. Description of Related Art
In semiconductor device manufacturing processes, contaminants attached to the peripheral portion of a semiconductor wafer may have nonnegligible influence on the quality of the treated semiconductor wafer.
In the so-called batch treatment process, multiple semiconductor wafers are held in a vertical posture and immersed in treatment liquid. Hence, if contaminants are attached to the peripheral portion of each semiconductor wafer, the contaminants are dispersed into the treatment liquid and attached again to the device forming area on the front surface of the semiconductor wafer.
Therefore, in recent years, the need for cleaning the peripheral portions of substrates, such as semiconductor wafers, has increased.
As prior art regarding the cleaning of the peripheral portions of substrates, the configurations proposed in Document 1 (Japanese Unexamined Patent Publication No. 2003-197592), Document 2 (Japanese Unexamined Patent Publication No. 2003-151943) and Document 3 (U.S. Pat. No. 6,550,091) can be taken as examples.
Document 1 proposes a configuration in which a cylindrical brush is provided, and the outer circumferential face of the brush is made to contact with the peripheral end face of a substrate while the substrate is rotated, thereby removing contaminants attached to the peripheral end face of the substrate.
Document 2 proposes a configuration similar to the configuration proposed in Document 1, in which a cylindrical brush is pushed to the peripheral end face of a substrate, and the peripheral end face of the substrate is allowed to bite into the outer circumferential face of the brush so that contaminants attached to the peripheral end face of the substrate can be removed more satisfactorily regardless of the shape of the peripheral end face of the substrate. Furthermore, another configuration has been proposed in which a groove corresponding to the shape of the peripheral end face of the substrate is formed in the outer circumferential face of a brush and the peripheral end face of the substrate is fitted in the groove.
Document 3 proposes a configuration in which a groove into which the peripheral portion of a substrate can be fitted is formed in the outer circumferential surface of a cylindrical brush, the substrate is rotated while the peripheral portion of the substrate is fitted in this groove, and the brush is rotated around its central axis, whereby the peripheral areas (the ring-shaped areas with a predetermined width from respective peripheral edges on the front surface and the back surface of the substrate) on the front surface and the back surface and the peripheral end face of the substrate are cleaned.
According to the configurations proposed in Documents 1 and 2, contaminants attached to the peripheral end face of a substrate can be removed. However, since the brush does not make contact with the peripheral areas on the front surface and the back surface of the substrate, contaminants attached to the peripheral areas cannot be removed.
On the other hand, according to the configuration proposed in Document 3, the peripheral areas on the front surface and the back surface of a substrate can be cleaned. However, the cleaning width (the contact width of the brush) in the peripheral areas on the front surface and the back surface of the substrate cannot be changed easily. For solving this problem, it is conceivable to change the cleaning width in the peripheral areas on the front surface and the back surface of the substrate by changing the amount of insertion of the peripheral portion of the substrate into the groove of the brush. However, if the amount of insertion of the peripheral portion of the substrate into the groove of the brush is small, the brush does not make contact with the peripheral end face of the substrate and cannot clean the peripheral end face of the substrate. Hence, it is impossible to use the method of changing the amount of insertion of the peripheral portion of the substrate into the groove of the brush. Therefore, when the cleaning width in the peripheral portion is changed, the brush must be replaced with a brush having a groove with a different depth. This method is very troublesome.
Furthermore, if a substrate is deformed by warping, the pushing pressure to the upwardly deformed portion of the substrate received from the brush becomes different from the pushing pressure to the downwardly deformed portion of the substrate received from the brush. It may lead to other problems of uneven cleaning and nonuniform cleaning width.